The present invention relates to a relay connector for electrically connecting a core conductor of a coaxial connector to a terminal electrode which is provided on a surface of a board, and for electrically connecting a shell ground (GND) of the coaxial connector to a GND electrode which is provided on a back surface of the board, for the purpose of inspecting the board.
In designing and producing a high frequency circuit board or the like, it is necessary to evaluate its performance in a course of designing. Therefore, by electrically connecting a core conductor of a coaxial connector to a terminal electrode which is provided at an end of a surface of the board, and by electrically connecting a shell GND of the coaxial connector to a GND electrode which is provided at an end of a back surface of the board, evaluation of the performance is achieved on the basis of a high frequency signal which is obtained from the terminal electrode. On this occasion, in case where a structure for electrically connecting the core conductor of the coaxial connector to the terminal electrode and electrically connecting the shell GND of the coaxial connector to the GND electrode is formed by soldering work, the work is complicated. Moreover, a work for removing the coaxial connector which has been soldered and fixed, from the board is also complicated. In view of the above, a related-art relay connector in which the coaxial connector can be attached to the board, without soldering has been already proposed (refer to JP-A-2008-171801).
The related-art relay connector disclosed in JP-A-2008-171801 will be briefly described referring to FIGS. 9A to 11. FIGS. 9A, 9B and 9C are views showing an outer appearance of the related-art relay connector. FIG. 9A is a side view, FIG. 9B is a plan view, and FIG. 9C is a front view. FIG. 10 is a sectional view as seen from arrow marks A-A in FIG. 9B. FIG. 11 is an exploded perspective view of the relay connector as shown in FIGS. 9A to 9C. In the related-art relay connector as shown in FIGS. 9A to 11, a through hole 20a is provided in a main block 20 formed of conductive material, a dielectric member 22b projected from a shell GND 22a of a coaxial connector (an SMA connector, for example) 22 is inserted into the through hole 20a from a back surface, the shell GND 22a is fixed with screws to the back surface to be electrically connected, and further, a core conductor 22c which has come out by stripping off the dielectric member 22b is projected from a front surface of the main block 20. On this occasion, an end surface of the dielectric member 22b is at a substantially same position as the front surface of the main block 20 or at a slightly retreated position from the front surface. Moreover, an axial direction in which the core conductor 22c is projected is perpendicular to the front surface of the main block 20. Guide pins 24, 24 are uprightly provided in the main block 20 so as to extend downward, in parallel with the front surface of the main block 20. A GND block 26 formed of conductive material is provided with guide boles 26a, 26a into which the guide pins 24, 24 are inserted. By detachably inserting the guide pins 24, 24 into these guide holes 26a, 26a, the GND block 26 can relatively move with respect to the main block 20 in sliding contact with each other, in a linear direction parallel to the front surface of the main block 20. Further, the GND block 26 is provided with a board rest part 26b so as to be opposed to the core conductor 22c in such a manner that the board rest part 26b can move in a direction of approaching or separating from the core conductor 22c by the relative movement. Moreover, an insulating cover is provided on a surface of the main block 20 in contact with the core conductor 22c at an opposite side to the board rest part 26b, so that the core conductor may not be bent, when the board is clamped between the board rest part 26b and the core conductor 22c. 
Further, moving range regulating screws 32, 32 are passed through moving range regulating through holes 30a, 30a which are formed in a vertical direction in an operating member 30, so as to move within a determined range in an axial direction. Then, distal ends of the moving range regulating screws 32, 32 are screwed into the main block 20 at an opposite side to a position where the GND block 26 is provided with respect to the core conductor 22c, and erected, in such a manner that the operating member 30 can relatively move in a direction of approaching or separating from the main block 20 within a determined range. On this occasion, a direction of the GND block 26 approaching or separating from the core conductor 22c and a direction of the operating member 30 approaching or separating from the main block are parallel to each other. In addition, elastic springs 34, 34 as elastic members are provided in a contracted state between the operating member 30 and the main block 20, whereby the operating member 30 is elastically urged in a direction of separating from the main block 20. Still further, the operating member 30 and the GND block 26 are connected to each other by means of connecting members 38, 36 with connecting pins 36, 36. These connecting members 38, 38 allow the GND block 26 to move in a direction of approaching or separating with respect to the core conductor 22c in association with the movement of the operating member 30 in the approaching or separating direction. Still further, a leaf spring 40 having conductivity is fixed to the GND block 26 with small screws. The leaf spring 40 is slidably provided in elastic contact with the main block 20, and electrically connected thereto. It is to be noted that a lateral width W of the related-art relay connector is set to be 12.7 mm, for example, which is equal to the lateral width of the shell GND 22a. 
In the related-art relay connector disclosed in JP-A-2008-171801, the board is inserted between the core conductor 22c and the board rest part 26b, by enlarging a distance between the core conductor 22c and the board rest part 26b by the relative movement of the main block 20 and the GND block 26, and the board can be clamped between the core conductor 22c and the board rest part 26b by reducing the distance between them by the relative movement. Then, the core conductor 22c of the coaxial connector 22 is brought into contact with a terminal electrode provided on a surface of the board to be electrically connected, and a GND electrode provided on a back surface of the board is electrically connected to the shell GND 22a of the coaxial connector 22 by way of the GND block 26 having the board rest part 26b and the main block 20. In this manner, it is possible to easily electrically connect the board to the coaxial connector 22. Moreover, it is possible to easily detach the board which has been inserted between the core conductor 22c and the board rest part 26b, by enlarging the distance between them by the relative movement. The work is extremely easily done, because when the operating member 30 is pressed to move toward the main block 20 against elastic forces of the elastic members 34, 34, the board rest part 26b of the GND block 26 which is connected to the operating member 30 by means of the connecting members 38, 38 relatively moves in a direction of separating from the core conductor 22c, and the distance between the core conductor 22c and the board rest part 26b is enlarged, whereby the board can be inserted between them, and further, when the pressure on the operating member is released, the board can be clamped between the core conductor 22c and the board rest part 26b with the elastic forces.
The related-art relay connector disclosed in JP-A-2008-171801 as described above is excellent in that the coaxial connecter 22 can be electrically connected to the board through the simple work. However, the dielectric member 22b of the coaxial connector 22 to be inserted into the through hole 22a which is provided in the main block 20 is fairly long, and a slight gap is likely to occur between an inner peripheral surface of the through hole 22a and an outer peripheral surface of the dielectric member 22b. Consequently, there is such anxiety that constant impedance is not maintained between them. Moreover, a slight gap may occur also between the main block 20 and the shell GND 22a of the coaxial connector 22 which is fixed to the main block 20, in some cases, and continuity of the impedance is likely to be lost due to the gap too. As the results, a slight deterioration of characteristic value in a part of a frequency zone is observed in the related-art structure, as compared with the conventional structure in which the core conductor of the coaxial connector is electrically connected to the terminal electrode by soldering, and the shell GND of the coaxial connector is electrically connected to the GND electrode by soldering.